Salt, Concrete, and Steel

Here in the Bahamas, a great number of buildings are constructed with concrete and steel rebar. The photos below are all too common in many of the buildings and are the effects of salt and a method of building that needs to be updated.

The salt comes from the sand, which comes from the beaches or nearby areas and is used to make the concrete. Everyone knows salt and steel don't play well together.

Another factor is that the steel rebar was more than likely left out and had already started to rust by the time it was installed. Once steel starts to rust, it will continue to rust.

Another bit of misinformation is that concrete is waterproof and the water can't get to the steel. Concrete is porous and will absorb a certain amount of water.

As the steel continues to rust, as shown above, it starts to expand and flake apart. This in return starts to push the concrete out until it falls off, as in the first photos.

Yet there are solutions that could help avoid this situation—and of course washing the sand would be a definite step in the right direction. The next would be to use a coated steel, such as below. As long as the coating isn't chipped, the rusting process won't have started.

Another method is the use of fiberglass rebar versus steel, though things are very slow to be adapted here and cost is always a factor. This also solves the resulting issue while providing the needed strength.

Another thing that should be avoided at all costs is the steel's proximity to the outer edge of the concrete. This is just a post but illustrates what happens when the steel is too close to the outer edge of the concrete: it blows out the concrete.

So if you find yourself building with concrete at any point, you now have some things to look out for to ensure the longevity of your home.